Process for making low compression and high airflow mdi viscoelastic polyurethane foam

ABSTRACT

A reaction system comprising an organic polyisocyanate and an isocyanate reactive component for preparation of a viscoelastic polyurethane foam is provided. The isocyanate reactive component comprises (i) from 10 to 50% by weight of one or more low equivalent weight propylene oxide rich (PO-rich) polyols having a combined number average equivalent weight from 200 to 500, (ii) from 45 to 95% by weight of one or more ethylene oxide (EO-rich) polyols having a combined number average equivalent weight from 200 to 800 and an ethylene oxide content from 40% to 65% by weight of the total mass of the EO-rich polyol and at least one of (iii) from 10 to 30% by weight of one or more high equivalent weight PO-rich polyols having a number average equivalent weight from 800 to 2,000 or (iv) from 10 to 40% by weight of one or more propylene oxide co-polymer polyols containing styrene-acrylonitrile.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to polyurethane foams. Moreparticularly, embodiments of the present invention relate topolyurethane foams having viscoelastic properties.

2. Description of the Related Art

Polyurethane foams are used in a wide variety of applications, rangingfrom cushioning (such as mattresses, pillows and seat cushions) topackaging to thermal insulation and for medical applications.Polyurethanes have the ability to be tailored to particular applicationsthrough the selection of the raw materials that are used to form thepolymer.

One class of polyurethane foam is known as viscoelastic (VE) or “memory”foam. Viscoelastic foams exhibit a time-delayed and rate-dependentresponse to an applied stress. They have low resiliency and recoverslowly when compressed. These properties are often associated with theglass transition temperature (Tg) of the polyurethane. Viscoelasticityis often manifested when the polymer has a Tg at or near the usetemperature, which is room temperature for many applications.

Like most polyurethane foams, VE polyurethane foams are prepared by thereaction of a polyol component with a polyisocyanate in the presence ofa blowing agent. The blowing agent is usually water or a mixture ofwater and another material. VE formulations are often characterized bythe selection of polyol component and the amount of water in theformulation. The predominant polyol used in these formulations has afunctionality of about 3 hydroxyl groups/molecule and a molecular weightin the range of 400-1500. This polyol is primarily the principaldeterminant of the Tg of the polyurethane foam, although other factorssuch as water levels and isocyanate index also play significant roles.

Typically, viscoelastic polyurethane foams have low air flow properties,generally less than about 1.0 standard cubic feet per minute (scfm)(0.47 liters/second) under conditions of room temperature (22° C.) andatmospheric pressure (1 atm), therefore promoting sweating when used ascomfort foams (for instance, bedding, seating and other cushioning). Lowair flow also leads to low heat and moisture transfer out of the foamresulting in (1) increased foam (bed) temperature and (2) moisturelevel. The consequence of higher temperature is higher resiliency andlowered viscoelastic character. Combined heat and moisture result inaccelerated fatigue of the foam. In addition, if foam air flows aresufficiently low, foams can suffer from shrinkage during manufacturing.Furthermore, improving the support factor of viscoelastic foams islimited unless viscoelastic properties are compromised.

High air flow may be obtained at the sacrifice of other physicalproperties such as compression set and tear. Low compression set iscritical for foam recovery from tight packing during storage andtransportation and reflects long term durability of foam articles suchas mattresses and pillows.

It would be desirable to achieve a higher air flow value than isgenerally now achieved while retaining viscoelastic properties of thefoam. Furthermore, it would be desirable to have foams with improved airflow while retaining properties such as compression set. In someapplications, it is also desirable to have foams which feel soft to thetouch.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to polyurethane foams. Moreparticularly, embodiments of the present invention relate topolyurethane foams having high air flow while maintaining viscoelasticproperties.

In one embodiment, a reaction system for preparation of viscoelasticpolyurethane foam is provided. The reaction system comprises (a) anorganic polyisocyanate and (b) an isocyanate reactive component. Theisocyanate reactive component comprises (i) from 10 to 50% by weight ofthe isocyanate reactive component of one or more low equivalent weightpropylene oxide rich (PO-rich) polyols having a combined number averageequivalent weight from 200 to 500, (ii) from 45 to 95% by weight of theisocyanate reactive component of one or more ethylene oxide (EO-rich)polyols having a combined number average equivalent weight from 200 to800 and an ethylene oxide content from 30% to 75% by weight of the totalmass of the EO-rich polyol and at least one of (iii) from 10 to 30% byweight of the isocyanate reactive component of one or more highequivalent weight PO-rich polyols having a number average equivalentweight from 800 to 2,000 and (iv) from 10 to 40% by weight of theisocyanate reactive component of one or more propylene oxide co-polymerpolyols containing styrene-acrylonitrile.

In another embodiment, a method of preparing viscoelastic foam isprovided. The method comprises forming reaction components and combiningthe reaction components at conditions sufficient to form a viscoelasticpolyurethane foam. The reaction components comprise an organicpolyisocyanate, an isocyanate reactive component, water, and a catalystcomponent. The isocyanate reactive component comprises one or more lowequivalent weight propylene oxide rich (PO-rich) polyols having acombined number average equivalent weight from 200 to 500 comprisingfrom 10 to 50% by weight of the isocyanate reactive component, one ormore ethylene oxide (EO-rich) polyols having a combined number averageequivalent weight from 200 to 800 and an ethylene oxide content from 40%to 65% by weight of the total mass of the EO-rich polyol comprising from45 to 95% by weight of the isocyanate reactive component, and at leastone of: (i) one or more high equivalent weight PO-rich polyols having anumber average equivalent weight from 800 to 2,000 comprising from 10 to30% by weight of the isocyanate reactive component, and (ii) one or morepropylene oxide co-polymer polyols containing styrene-acrylonitrile from10 to 40% by weight of the isocyanate reactive component.

In yet another embodiment, a reaction system for preparation of aviscoelastic polyurethane foam is provided. The reaction systemcomprises (a) an organic polyisocyanate, (b) an isocyanate reactivecomponent, and (c) an organosilicone surfactant. The isocyanate reactivecomponent comprises ((b)(i)) from 70% to 95% by weight of the isocyanatereactive component of one or more ethylene oxide (EO-rich) polyolshaving a combined number average equivalent weight from 200 to 800 andan ethylene oxide content from 40% to 65% by weight of the total mass ofthe EO-rich polyol and ((b)(ii)) from 10% to 30% by weight of theisocyanate reactive component of one or more high equivalent weightpropylene oxide rich (PO-rich) polyols having a number averageequivalent weight from 800 to 2,000.

DETAILED DESCRIPTION

Embodiments of the present invention relate to polyurethane foams. Moreparticularly, embodiments of the present invention relate topolyurethane foams having high air flow while maintaining viscoelasticproperties.

As used herein, the term “air flow” refers to the volume of air whichpasses through a 1.0 inch (2.54 cm) thick 2 inch×2 inch (5.08 cm) squaresection of foam at 125 Pa (0.018 psi) of pressure. Units are expressedin cubic decimeters per second (i.e. liters per second) and converted tostandard cubic feet per minute. A representative commercial unit formeasuring air flow is manufactured by TexTest AG of Zurich, Switzerlandand identified as TexTest Fx3300. This measurement follows ASTM D 3574Test G.

As used herein, the term “CFD 25%” refers to a compression forcedeflection measurement where a foam 4×4 inches in the lateral directionand 2 inches thick (10.16×10.16×5.08 cm) is compressed down in thethickness-axis to a compression strain of 25%, and held for one minutebefore the compression force deflection measurement is determined, i.e.,the foam is compressed to 75%, of its original thickness, according tothe procedures of ASTM D 3574 C and is measured in pounds force (lbf),newtons (N), or kilopascals (kPa). “CFD 40%”, “CFD 65%” and “CFD 75%”similarly corresponds to a compression to 60%, 35% and 25% of theoriginal foam thickness, respectively.

As used herein, the term “Compression Set @ 90%” stands for compressionset test measured at the 90% compressive deformation level and parallelto the rise direction in the foam. This test is used herein to correlatein-service loss of cushion thickness and changes in foam hardness. Thecompression set is determined according to the procedures of ASTM D3574-95, Test I, and is measured as percentage of original thickness ofthe sample.

As used herein, the term “density” is used herein to refer to weight perunit volume of a foam. In the case of viscoelastic polyurethane foamsthe density is determined according to the procedures of ASTM D357401,Test A. Advantageously, the viscoelastic foam has a density of at leastabout 2.5, preferably at least about 3, more preferably at least about 4and preferably at most about 8, more preferably at most about 6, mostpreferably at most about 5.5 pounds/ft³ (40, 48, 64, 128, 96, 88 kg/m³,respectively).

As used herein, the term “elongation %” as applied to a foam is usedherein to refer to the linear extension which a sample of foam canattain before rupture. The foam is tested by the same method used todetermine tensile strength, and the result is expressed as a percentageof the original length of the foam sample according to the procedures ofASTM D-3574, Test E.

As used herein, the term “functionality” particularly “polyolfunctionality” is used herein to refer to the number of active hydrogenson an initiator, used to prepare the polyol, that can react with anepoxide molecule (such as ethylene oxide or propylene oxide). This isalso referred to as nominal functionality. For the purpose of polyolfunctionality, any primary/secondary amine or hydroxyl functionalitywill count once toward the nominal functionality value.

As used herein, the term “Indentation Force Deflection” (IFD) is ameasure of load bearing and is expressed in Newtons or pound-force(lbf). As used herein, the term “25% IFD” refers to a measure of theforce required to make a dent 1 inch (25% of the thickness) into a foamsample 15″×15″×4″ by an 8 inch diameter (50 in²) disc. The testingdevice records the force in pounds required to hold the foam indenterafter one minute. As used herein, the term “65% IFD” refers to the forcerequired to make a dent 65% of the thickness into a foam sample15″×15″×4″ by an 8 inch diameter (50 in²) disc.

As used herein, the term “VE Recovery Time” or “Recovery Time”, ismeasured by releasing/returning the compression load head from the VE75% position (foam compression to 25% of original foam thickness) to theposition where foam compression is to 90% of original foam thickness.The Recovery Time is defined as the time from releasing/returning thecompression load head to the moment that the foam pushes back againstthe load head with a force of at least one Newton. The Recovery Time isdetermined according to the procedures of ASTM D-3574M and is measuredin seconds. For a viscoelastic foam this time is desirably at leastabout 2 seconds, preferably at least about 5 seconds and most preferablyat least about 6 seconds, but advantageously less than about 30 secondsand preferably less than about 20 seconds. This is one measure of the“shape memory effect” although it is not absolute, since one can get alow number on the Recovery Time and still have a “shape memory foam

As used herein, the term “resiliency” is used to refer to the quality ofa foam perceived as springiness. It is measured according to theprocedures of ASTM D3574 Test H. This ball rebound test measures theheight a dropped steel ball of known weight rebounds from the surface ofthe foam when dropped under specified conditions and expresses theresult as a percentage of the original drop height. As measuredaccording to the ASTM test, a cured VE foam exhibits a resiliency ofadvantageously at most about 20%, preferably at most about 10%.

As used herein, the term “support factor” refers to the ratio of 65%Compression Force Deflection (CFD) divided by 25% Compression ForceDeflection.

As used herein, the term “tear strength” is used herein to refer to themaximum average force required to tear a foam sample which ispre-notched with a slit cut lengthwise into the foam sample. The testresults are determined according to the procedures of ASTM D3574-F inpounds per linear inch (lb_(f)/in) or in newtons per meter (N/m).

As used herein, the term “viscoelastic foam” is intended to designatethose foams having a resilience of less than 25%, as measured accordingto ASTM D3574 Test H. Preferably the foam will have a resilience of lessthan 20%. In certain embodiments the foam will have a resilience of lessthan 15% or even less than 10%.

The isocyanate-reactive components used in polyurethane production aregenerally those compounds having at least two hydroxyl groups. Thosecompounds are referred to herein as polyols. The polyols include thoseobtained by the alkoxylation of suitable starting molecules (initiators)with an alkylene oxide. Examples of initiator molecules having 2 to 4reactive sites include water, ammonia, or polyhydric alcohols such asdihydric alcohols having a molecular weight from 62 to 399, especiallythe alkane polyols such as ethylene glycol, propylene glycol,hexamethylene diol, glycerol, trimethylol propane or trimethylol ethane,or low molecular weight alcohols containing ether groups such asdiethylene glycol, triethylene glycol, dipropylene glycol, tripropyleneglycol or butylene glycols. These polyols are conventional materialsprepared by conventional methods. For polyols, when the term “triol” or“monol” is used, the functionality of the starting initiator (such asglycerin for triols and n-butanol for monols) is intended. Catalysis forthis polymerization can be either anionic or cationic, with catalystssuch as potassium hydroxide (KOH), cesium hydroxide (CsOH), borontrifluoride, or a double metal cyanide complex (DMC) catalyst such aszinc hexacyanocobaltate or quaternary phosphazenium compound. In thecase of alkaline catalysts, these alkaline catalysts are preferablyremoved from the polyol at the end of production by a proper finishingstep, such as coalescence, magnesium silicate separation or acidneutralization.

In one embodiment, a reaction system for preparation of a viscoelasticpolyurethane foam is provided. The reaction system comprises (a) one ormore methylene diphenyl diisocyanate (MDI) based components and (b) anisocyanate reactive component. In certain embodiments, the reactionsystem further comprises (c) one or more blowing agents. In certainembodiments, the reaction system further comprises (d) one or morecatalyst components. In certain embodiments, the reaction system furthercomprises (e) one or more surfactants. In certain embodiments, thereaction system further comprises additional additives.

Component (a) may comprise one or more organic polyisocyanate componentshaving an average of 1.8 or more isocyanate groups per molecule. Theisocyanate functionality is preferably from about 1.9 to 4, and morepreferably from 1.9 to 3.5 and especially from 2.0 to 3.3.

The one or more organic polyisocyanate components may be a polymericpolyisocyanate, aromatic isocyanate, cycloaliphatic isocyanate, oraliphatic isocyanate. Exemplary polyisocyanates include m-phenylenediisocyanate, tolulene-2,4-diisocyanate, tolulene-2,6-diisocyanate,hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate,cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate,naphthylene-1,5-diisocyanate, methoxyphenyl-2,4-diisocyanate,diphenylmethane-4,4′-diisocyanate, 4,4′-biphenylene diisocyanate,3,3′-dimethoxy-4,4′-biphenyl diisocyanate, 3,3′-dimethyl-4-4′-biphenyldiisocyanate, 3,3′-dimethyldiphenyl methane-4,4′-diisocyanate,4,4′,4″-triphenyl methane triisocyanate, a polymethylenepolyphenylisocyanate (PMDI), toluene-2,4,6-triisocyanate and4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate. Preferredpolyisocyanates include MDI and derivatives of MDI such as biuretmodified “liquid” MDI products and polymeric MDI. Preferredpolyisocyanates are the so-called polymeric MDI products, which are amixture of polymethylene polyphenylene polyisocyanates in monomeric MDI.In one embodiment, the polymeric MDI comprises 70 wt. % or more of thetotal isocyanate. Especially suitable polymeric MDI products have a freeMDI content of from 5 to 50% by weight, more preferably 10 to 40% byweight. Such polymeric MDI products are available from The Dow ChemicalCompany under the trade names PAPI® and VORANATE®.

An especially preferred polyisocyanate is a polymeric MDI product havingan average isocyanate functionality of from 2.3 to 3.3 isocyanategroups/molecule and an isocyanate equivalent weight from 120 to 170,preferably from 125 to 135. Suitable commercially available products ofthat type include PAPI™ PB-219, PAPI™ 27, Voranate™ M229, Voranate™ 220,Voranate™ 290, Voranate™ M595 and Voranate™ M600, all of which areavailable from The Dow Chemical Company.

The amount of polyisocyanate that is used typically is sufficient toprovide an isocyanate index of from 55 to 110. In yet another embodimentthe index is from 60 to 110. In yet another embodiment the index is from70 to 100 and in a further embodiment from 75 to 90.

Component (b) may be an isocyanate reactive component comprising (i)from 10 to 50% by weight of the isocyanate reactive component of one ormore low equivalent weight propylene oxide rich (PO-rich) polyols havinga combined number average equivalent weight from 200 to 500, (ii) from50 to 95% by weight of the isocyanate reactive component of one or moreethylene oxide (EO-rich) polyols having a combined number averageequivalent weight from 200 to 800 and an ethylene oxide content equal toor greater than 30% but less than 70% of the total mass of the EO-richpolyol, and either (iii) from 10 to 30% by weight of the isocyanatereactive component of one or more high equivalent weight PO-rich polyolshaving a number average equivalent weight from 800 to 2,000, or (iv)from 10 to 40% by weight of the isocyanate reactive component of one ormore propylene oxide co-polymer polyols containingstyrene-acrylonitrile. In certain embodiments, the isocyanate reactivecomponent (b) further comprises (v) from 5 to 10% by weight of theisocyanate reactive component of one or more ethylene oxide-propyleneoxide monols having a combined number average equivalent weight from 300to 800.

In certain embodiments the low equivalent weight PO-rich polyol ((b)(i))may comprise at least 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %,35 wt. %, 40 wt. %, or 45 wt. % of the total isocyanate reactivecomponent (b). In certain embodiments, the one or more low equivalentweight PO-rich polyols ((b)(i)) may comprise up to 15 wt. %, 20 wt. %,25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. % or 50 wt. % of thetotal isocyanate reactive component (b). In certain embodiments, the oneor more low equivalent weight PO-rich polyols ((b)(i)) may comprise from10% to 50% by weight or from about 20% to 40% by weight of the totalisocyanate reactive component (b).

In certain embodiments, the one or more low equivalent weight PO-richpolyols ((b)(i)) have a combined number average equivalent weight from200 to 500. In certain embodiments, the one or more low equivalentweight PO-rich polyols ((b)(i)) have a combined number averageequivalent weight from 200 to 340. In certain embodiments, the one ormore low equivalent weight PO-rich polyols ((b)(i)) have a functionalitybetween 2 and 6. In certain embodiments, the one or more low equivalentweight PO-rich polyols ((b)(i)) have a functionality between 2.2 and 4.In certain embodiments, the one or more low equivalent weight PO-richpolyols ((b)(i)) have a PO content of at least 70 wt. %, 75 wt. %, 80wt. %, 85 wt. %, 90 wt. %, or 95 wt. % of the total mass of the lowequivalent weight PO-rich polyol. In certain embodiments, the one ormore low equivalent weight PO-rich polyols ((b)(i)) have a PO content ofup to 75 wt. %, 80 wt. %, 85 wt. %, 90 wt. %, 95 wt. % or 100 wt. % ofthe total mass of the low equivalent weight PO-rich polyol. In certainembodiments, the one or more low equivalent weight PO-rich polyols((b)(i)) will have some amount of primary hydroxyl content. In certainembodiments, the one or more low equivalent weight PO-rich polyols willhave a primary hydroxyl content of 30% or greater of the total hydroxylcontent of the low equivalent weight PO-rich polyol.

In certain embodiments, the one or more EO-rich polyols ((b)(ii)) maycomprise at least 45 wt. %, 50 wt. %, 55 wt. %, 60 wt. %, 65 wt. %, 70wt. %, 75 wt. %, 80 wt. %, 85 wt. % or 90 wt. % of the total isocyanatereactive component (b). In certain embodiments, the one or more EO-richpolyols ((b)(ii)) may comprise up to 50 wt. %, 55 wt. %, 60 wt. %, 65wt. %, 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, 90 wt. %, or 95 wt. %.The one or more EO-rich polyols ((b)(ii)) may comprise from 45 wt. % to95 wt. % by weight or from 65 wt. % to 85 wt. % of the total isocyanatereactive component (b).

In certain embodiments, the one or more EO-rich polyols ((b)(ii)) have acombined number average equivalent weight from 200 to 800. In certainembodiments, the one or more EO-rich polyols ((b)(ii)) have a combinednumber average equivalent weight from 250 to 400. In certainembodiments, the one or more EO-rich polyols ((b)(ii)) have afunctionality between 2 and 6. In certain embodiments, the one or moreEO-rich polyols ((b)(ii)) have a functionality between 2.5 and 4. Incertain embodiments, the one or more EO-rich polyols ((b)(ii)) have anEO content of at least 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50 wt. %,55 wt. %, 60 wt. %, 65 wt. %, or 70 wt. % of the total mass of the oneor more EO-rich polyols. In certain embodiments, the one or more EO-richpolyols ((b)(ii)) have an EO content of up to 35 wt. %, 40 wt. %, 45 wt.%, 50 wt. %, 55 wt. %, 60 wt. %, 65 wt. %, 70 wt. %, or 75 wt. % of thetotal mass of the one or more EO-rich polyols. The one or more EO-richpolyols ((b)(ii)) may have an EO content greater than 30% but less than75% of the total mass of the one or more EO-rich polyols or from 40 wt.% to 65 wt. % of the total mass of the one or more EO-rich polyols orfrom 50 wt. % to 60 wt. % of the total mass of the one or more EO-richpolyols. In certain embodiments, the one or more EO-rich polyols((b)(ii) have a primary hydroxyl content of less than 50%.

In certain embodiments where molded foams are produced the one or moreEO-rich polyols ((b)(ii)) may have a combined number average equivalentweight from 200 to 800, preferably from 350 to 550. In certainembodiments where molded foams are produced, the one or more EO-richpolyols ((b)(ii)) may have an EO content from 30% to 75% of the totalmass of the one or more EO-rich polyols.

In certain embodiments, the one or more high equivalent weight PO-richpolyols ((b)(iii)) may comprise at least 10 wt. %, 15 wt. %, 20 wt. %,or 25 wt. % of the total isocyanate reactive component (b). In certainembodiments, the one or more high equivalent weight PO-rich polyols((b)(iii)) may comprise up to 15 wt. %, 20 wt. %, 25 wt. %, or up to 30wt. % of the total isocyanate reactive component (b). In certainembodiments, the one or more high equivalent weight PO-rich polyols((b)(iii)) may comprise from 10% to 30% by weight or from about 15% to20% by weight of the total isocyanate reactive component (b).

In certain embodiments, the one or more high equivalent weight PO-richpolyols ((b)(iii)) have a combined number average equivalent weight from800 to 2,000. In certain embodiments, the one or more high equivalentweight PO-rich polyols ((b)(iii)) have a combined number averageequivalent weight from 900 to 1,200. In certain embodiments, the one ormore high equivalent weight PO-rich polyols ((b)(iii)) have afunctionality between 2 and 6. In certain embodiments, the one or morehigh equivalent weight PO-rich polyols ((b)(iii)) have a functionalitybetween 2.2 and 4. In certain embodiments, the one or more highequivalent weight PO-rich polyols ((b)(iii)) have a PO content of atleast 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, 90 wt. %, or 95 wt. % ofthe total mass of the low equivalent weight PO-rich polyol. In certainembodiments, the one or more low equivalent weight PO-rich polyols((b)(iii)) have a PO content of up to 75 wt. %, 80 wt. %, 85 wt. %, 90wt. %, 95 wt. % or 100 wt. % of the total mass of the low equivalentweight PO-rich polyol.

In certain embodiments, the one or more propylene oxide co-polymerpolyols ((b)(iv)) may comprise at least 10 wt. %, 15 wt. %, 20 wt. %, or25 wt. % of the total isocyanate reactive component (b). In certainembodiments, the one or more propylene oxide co-polymer polyols((b)(iv)) may comprise up to 15 wt. %, 20 wt. %, 25 wt. %, or up to 30wt. % of the total isocyanate reactive component (b). In certainembodiments, the one or more propylene oxide co-polymer polyols((b)(iv)) may comprise from 10% to 30% by weight or from about 15% to20% by weight of the total isocyanate reactive component (b).

In certain embodiments, the propylene oxide co-polymer polyol ((b)(iv))contains dispersed polymer particles. In certain embodiments, propyleneoxide co-polymer polyol ((b)(iv)) contains dispersedstyrene/acrylonitrile (SAN) particles. In certain embodiments, thedispersed polymer particles are obtained by in-situ polymerization ofacrylonitrile and styrene. In certain embodiments, the one or morepropylene oxide co-polymer polyols ((b)(iv)) comprise from 20% to 50%solid styrene acrylonitrile. In certain embodiments, the one or morepropylene oxide co-polymer polyols ((b)(iv)) comprise from 30% to 40%solid styrene acrylonitrile. In certain embodiments, the styreneacrylonitrile particles have a particle size from 1 to 2 microns. Incertain embodiments, the one or more propylene-oxide polyols have ahydroxyl number of 22.

In certain embodiments, the one or more ethylene oxide-propylene oxidemonols ((b)(v)) may comprise at least 1 wt. %, 5 wt. %, 10 wt. %, or 15wt. % of the total isocyanate reactive component (b). In certainembodiments, the one or more ethylene oxide-propylene oxide monols((b)(v)) may comprise up to 5 wt. %, 10 wt. %, 15 wt. %, or 20 wt. % ofthe total isocyanate reactive component (b). In certain embodiments, theone or ethylene oxide-propylene oxide monols ((b)(v)) may comprise from1% to 20% by weight or from 5% to 10% by weight of the total isocyanatereactive component (b).

In certain embodiments, the one or more ethylene oxide-propylene oxidemonols ((b)(v)) have an equivalent weight from 300 to 800. In certainembodiments, the one or more ethylene oxide-propylene oxide monols((b)(v)) have an equivalent weight from 400 to 600. In certainembodiments, the one or more ethylene oxide-propylene oxide monols((b)(v)) have a functionality between 1 and 2. In certain embodiments,the one or more ethylene oxide-propylene oxide monols ((b)(v)) have anEO content from 30-70% of the total mass of the copolymer. In certainembodiments, the one or more ethylene oxide-propylene oxide monols((b)(v)) have an EO content from 40-60% of the total mass of thecopolymer. In certain embodiments, the one or more ethyleneoxide-propylene oxide monols ((b)(iv)) are selected from random blockcopolymers (RBC) and block copolymers.

Not to be limited by theory, but it is believed that the one or moreethylene oxide-propylene oxide monols ((b)(v)) help with thecompatibility of the PO-rich and EO-rich polyols as well as contributingto improved cell opening and air flow.

In certain embodiments, the low equivalent weight PO-rich polyol ((b)(i)and the high equivalent weight PO-rich polyol ((b)(iii)) may be combinedto form a single PO-rich polyol component. In certain embodiments, thesingle PO-rich polyol component has a combined number average equivalentweight from 210 to 450 and preferably from 240 to 400. In certainembodiments, the single PO-rich polyol has a functionality from 2.4 to4.0.

In certain embodiments, the single PO-rich polyol comprises at least 5wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40wt. %, or 45 wt. % of the total isocyanate reactive component (b). Incertain embodiments, the single PO-rich polyol comprises up to 10 wt. %,15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, orup to 50 wt. % of the total isocyanate reactive component (b). Incertain embodiments, the single PO-rich polyol may comprise from 5% to50% by weight or from about 15% to 35% by weight of the total isocyanatereactive component (b).

In certain embodiments, the isocyanate reactive component (b) mayfurther comprise a chain extender ((b)(vi)). A chain extender is amaterial having two isocyanate-reactive groups per molecule. In eithercase, the equivalent weight per isocyanate-reactive group can range fromabout 30 to less than 100, and is generally from 30 to 75. Theisocyanate-reactive groups are preferably aliphatic alcohol, primaryamine or secondary amine groups, with aliphatic alcohol groups beingparticularly preferred. The chain extender ((b)(vi)) is typically usedin small quantities such as up to 10 parts, especially up to 2 parts, byweight per 100 parts by weight of the total reactive system. In certainembodiments, the chain extender ((b)(vi)) content is from 0.015 to 5% byweight of the isocyanate reactive component (b). Examples of chainextenders include alkylene glycols such as ethylene glycol, 1,2- or1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and the like;glycol ethers such as diethylene glycol.

In certain embodiments the isocyanate reactive component (b) comprises((b)(i)) from 70% to 95% by weight of the isocyanate reactive componentof one or more ethylene oxide (EO-rich) polyols having a combined numberaverage equivalent weight from 200 to 800 and an ethylene oxide contentfrom 40% to 65% by weight of the total mass of the EO-rich polyol and((b)(ii)) from 10% to 30% by weight of the isocyanate reactive componentof one or more high equivalent weight propylene oxide rich (PO-rich)polyols having a number average equivalent weight from 800 to 2,000.

In certain embodiments, the one or more EO-rich polyols ((b)(i))(described above as ((b)(ii)) may comprise at least 70 wt. %, 75 wt. %,80 wt. %, 85 wt. %, or 90 wt. % of the total isocyanate reactivecomponent (b). In certain embodiments, the one or more EO-rich polyols((b)(ii)) may comprise up to 75 wt. %, 80 wt. %, 85 wt. %, 90 wt. %, or95 wt. %. The one or more EO-rich polyols ((b)(ii)) may comprise from 70wt. % to 95 wt. % by weight or from 75 wt. % to 85 wt. % of the totalisocyanate reactive component (b).

In certain embodiments, the one or more high equivalent weight PO-richpolyols ((b)(ii)) (described above as ((b)(iii)) may comprise at least10 wt. %, 15 wt. %, 20 wt. %, or 25 wt. % of the total isocyanatereactive component (b). In certain embodiments, the one or more highequivalent weight PO-rich polyols ((b)(iii)) may comprise up to 15 wt.%, 20 wt. %, 25 wt. %, or up to 30 wt. % of the total isocyanatereactive component (b). In certain embodiments, the one or more highequivalent weight PO-rich polyols ((b)(iii)) may comprise from 10% to30% by weight or from about 20% to 25% by weight of the total isocyanatereactive component (b).

In certain embodiments, the reaction system further comprises (c) ablowing agent. In certain embodiments, the blowing agent content is from1% to 5% by weight of the total weight of the reaction system. Incertain embodiments, the blowing agent content is from 1% to 2% byweight of the total weight of the reaction system. In certainembodiments, the blowing agent is water.

In certain embodiments, the reaction system further comprises (d) one ormore catalysts. Catalysts are typically used in small amounts, forexample, each catalyst being employed from 0.0015 to 5% by weight of thetotal reaction system. The amount depends on the catalyst or mixture ofcatalysts, the desired balance of the gelling and blowing reactions forspecific equipment, the reactivity of the polyols and isocyanate as wellas other factors familiar to those skilled in the art.

A wide variety of materials are known to catalyze polyurethane formingreactions, including tertiary amines; tertiary phosphines such astrialkylphosphines and dialkylbenzylphosphines; various metal chelatessuch as those which can be obtained from acetylacetone, benzoylacetone,trifluoroacetyl acetone, ethyl acetoacetate and the like, with metalssuch as Be, Mg, Zn, Cd, Pd, Ti, Zr, Sn, As, Bi, Cr, Mo, Mn, Fe, Co andNi; acid metal salts of strong acids, such as ferric chloride, stannicchloride, stannous chloride, antimony trichloride, bismuth nitrate andbismuth chloride; strong bases such as alkali and alkaline earth metalhydroxides, alkoxides and phenoxides, various metal alcoholates andphenolates such as Ti(OR)₄, Sn(OR)₄ and Al(OR)₃, wherein R is alkyl oraryl, and the reaction products of the alcoholates with carboxylicacids, beta-diketones and 2-(N,N-dialkylamino)alcohols; alkaline earthmetal, Bi, Pb, Sn or Al carboxylate salts; and tetravalent tincompounds, and tri- or pentavalent bismuth, antimony or arseniccompounds. Preferred catalysts include tertiary amine catalysts andorganotin catalysts. Examples of commercially available tertiary aminecatalysts include: trimethylamine, triethylamine, N-methylmorpholine,N-ethylmorpholine, N,N-dimethylbenzylamine, N,N-dimethylethanolamine,N,N-dimethylaminoethyl, N,N,N′,N′-tetramethyl-1,4-butanediamine,N,N-dimethylpiperazine, 1,4-diazobicyclo-2,2,2-octane,bis(dimethylaminoethyl)ether, triethylenediamine and dimethylalkylamineswhere the alkyl group contains from 4 to 18 carbon atoms. Mixtures ofthese tertiary amine catalysts are often used.

Examples of commercially available amine catalysts include NIAX™ A1 andNIAX™ A99 (bis(dimethylaminoethyl)ether in propylene glycol availablefrom Momentive Performance Materials), NIAX™ B9 (N,N-dimethylpiperazineand N-N-dimethylhexadecylamine in a polyalkylene oxide polyol, availablefrom Momentive Performance Materials), DABCO® 8264 (a mixture ofbis(dimethylaminoethyl)ether, triethylenediamine anddimethylhydroxyethyl amine in dipropylene glycol, available from AirProducts and Chemicals), DABCO 33LV® (triethylene diamine in dipropyleneglycol, available from Air Products and Chemicals), DABCO® BL-11 (a 70%bis-dimethylaminoethyl ether solution in dipropylene glycol, availablefrom Air Products and Chemicals, Inc), NIAX™ A-400 (a proprietarytertiary amine/carboxylic salt and bis (2-dimethylaminoethy)ether inwater and a proprietary hydroxyl compound, available from MomentivePerformance Materials); NIAX™ A-300 (a proprietary tertiaryamine/carboxylic salt and triethylenediamine in water, available fromMomentive Performance Materials); POLYCAT® 58 (a proprietary aminecatalyst available from Air Products and Chemicals), POLYCAT® 5(pentamethyl diethylene triamine, available from Air Products andChemicals) and POLYCAT® 8 (N,N-dimethyl cyclohexylamine, available fromAir Products and Chemicals).

Examples of organotin catalysts are stannic chloride, stannous chloride,stannous octoate, stannous oleate, dimethyltin dilaurate, dibutyltindilaurate, other organotin compounds of the formula SnR_(n)(OR)_(4-n),wherein R is alkyl or aryl and n is 0-2, and the like. Organotincatalysts are generally used in conjunction with one or more tertiaryamine catalysts, if used at all. Commercially available organotincatalysts of interest include KOSMOS® 29 (stannous octoate from EvonikAG), DABCO® T-9 and T-95 catalysts (both stannous octoate compositionsavailable from Air Products and Chemicals).

In certain embodiments, the reaction system further comprises (e) one ormore surfactants to help stabilize the foam as it expands and cures.Surfactants are typically used in small amounts, for example, eachcatalyst being employed from about 0.0015 to about 5% by weight of thetotal reaction system. The amount depends on the surfactants or mixtureof surfactants, as well as other factors familiar to those skilled inthe art.

Examples of surfactants include nonionic surfactants and wetting agentssuch as those prepared by the sequential addition of propylene oxide andthen ethylene oxide to propylene glycol, solid or liquidorganosilicones, and polyethylene glycol ethers of long chain alcohols.Ionic surfactants such as tertiary amine or alkanolamine salts of longchain alkyl acid sulfate esters, alkyl sulfonic esters and alkylarylsulfonic acids may also be used. The surfactants prepared by thesequential addition of propylene oxide and then ethylene oxide topropylene glycol are preferred, as are the solid or liquidorganosilicones. Examples of useful organosilicone surfactants includecommercially available polysiloxane/polyether copolymers such asTEGOSTAB® (trademark of Evonik AG) B-8462, B-8404 and B-8871, and DC-198and DC-5043 surfactants, available from Dow Corning, and NIAX™ L-627,NIAX™ L-620, and NIAX™ L-618 available from Momentive PerformanceMaterials. Surprisingly, NIAX™ L-620 surfactant provides improved airflow in comparison to other silicone surfactants which enables the useof one or more PO-rich polyols having a higher average equivalentweight.

In a further embodiment, to improve processing and to permit the use ofhigher isocyanate indices, additional additives such as those describedin publication WO 20008/021034, the disclosure of which is incorporatedherein by reference, may be added to the reaction mixture. Suchadditives include 1) alkali metal or transition metal salts ofcarboxylic acids; 2) 1,3,5-tris alkyl- or 1,3,5-tris (N,N-dialkyl aminoalkyl)-hexahydro-s-triazine compounds; and 3) carboxylate salts ofquaternary ammonium compounds. When used, such additives are generallyused in an amount from about 0.01 to 1 part per 100 total polyol. Theadditional additive is generally dissolved in at least one othercomponent of the reaction mixture. It is generally not preferred todissolve it in the polyisocyanate.

Various additional components may be included in the viscoelastic foamformulation. These include, for example, crosslinkers, plasticizers,fillers, smoke suppressants, fragrances, reinforcements, dyes,colorants, pigments, preservatives, odor masks, physical blowing agents,chemical blowing agents, flame retardants, internal mold release agents,biocides, antioxidants, UV stabilizers, antistatic agents, thixotropicagents, adhesion promoters, cell openers, and combination of these.

The foamable composition may contain a cell opener or crosslinker. Whenthese materials used, they are typically used in small quantities suchas up to 10 parts, especially up to 2 parts, by weight per 100 parts byweight of the total reactive system. A cross-linker is a materialhaving, on average, greater than two isocyanate-reactive groups permolecule. In either case, the equivalent weight per isocyanate-reactivegroup can range from about 30 to less than 100, and is generally from 30to 75. The isocyanate-reactive groups are preferably aliphatic alcohol,primary amine or secondary amine groups, with aliphatic alcohol groupsbeing particularly preferred. Examples of chain extenders andcrosslinkers include alkylene glycols such as ethylene glycol, 1,2- or1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and the like;glycol ethers such as diethylene glycol.

One or more fillers may also be present in the viscoelastic foamformulation. A filler may help modify the composition's rheologicalproperties in a beneficial way, reduce cost and impart beneficialphysical properties to the foam. Suitable fillers include particulateinorganic and organic materials that are stable and do not melt at thetemperatures encountered during the polyurethane-forming reaction.Examples of suitable fillers include kaolin, montmorillonite, calciumcarbonate, mica, wollastonite, talc, high-melting thermoplastics, glass,fly ash, carbon black titanium dioxide, iron oxide, chromium oxide,azo/diazo dyes, phthalocyanines, dioxazines and the like. The filler mayimpart thixotropic properties to the foamable polyurethane composition.Fumed silica is an example of such a filler.

Reactive particles may also be included in the reaction system to modifythe properties of the viscoelastic foam. Such reactive systems includecopolymer polyols such as those containing styrene/acrylonitrile (SAN),polyharnstoff dispersion (PHD) polyols and polyisocyanate polyadditionproducts (PIPA), for instance as taught in Chemistry and Technology ofPolyols for Polyurethanes, Rapra Technology Limited (2005) pp 185-227.

When used, fillers advantageously constitute from about 0.5 to about30%, especially about 0.5 to about 10%, by weight of the reactionsystem.

Although no additional blowing agent (other than the water) in thefoamable polyurethane composition is generally used, it is within thescope of the embodiments described herein to include an additionalphysical or chemical blowing agent. The physical blowing agents can be,but are not limited to, liquid carbon dioxide (CO₂), supercritical CO₂and various hydrocarbons, fluorocarbons, hydrofluorocarbons,chlorocarbons (such as methylene chloride), chlorofluorocarbons andhydrochlorofluorocarbons. Chemical blowing agents are materials thatdecompose or react (other than with isocyanate groups) at elevatedtemperatures to produce carbon dioxide and/or nitrogen.

The VE foam can be prepared in a so-called slabstock process, or byvarious molding processes; refer to “Flexible Polyurethane Foams” by R.Herrington, ed., 1999. In a slabstock process, the components are mixedand poured into a trough or other region where the formulation reacts,expands freely in at least one direction, and cures. Slabstock processesare generally operated continuously at commercial scales.

In a slabstock process, the various components are introducedindividually or in various subcombinations into a mixing head, wherethey are mixed and dispensed. Component temperatures are generally inthe range of from 15 to 35° C. prior to mixing. The dispensed mixturetypically expands and cures without applied heat. In the slabstockprocess, the reacting mixture expands freely or under minimal restraint(such as may be applied due to the weight of a cover sheet or film).

It is also possible to produce the viscoelastic foam in a moldingprocess, by introducing the reaction mixture into a closed mold where itexpands and cures. Often times, the mold itself is pre-heated to atemperature above ambient conditions. Such pre-heating of the mold canlead to faster cycle time.

Viscoelastic foam made in accordance with the embodiments describedherein are useful in a variety of packaging and cushioning applications,such as mattresses, including mattress toppers, pillows, packaging,bumper pads, sport and medical equipment, helmet liners, pilot seats,earplugs, and various noise and vibration dampening applications. Thenoise and vibration dampening applications are of particular importancefor the transportation industry, such as in automotive applications.

The following examples are provided to illustrate embodiments of theinvention, but are not intended to limit the scope thereof. All partsand percentages are by weight unless otherwise indicated.

A description of the raw materials used in the examples is as follows.

Polyol A is a 3 functional, glycerin initiated, 336 equivalent weightall propylene oxide polyether polyol with a hydroxyl number of 167commercially available from The Dow Chemical Company under the tradedesignation VORANOL® 3150.

Polyol B is a poly ethylene oxide—co-propylene oxide copolymer triol(glycerin initiated), with 60 wt. % of ethylene oxide in the alkyleneoxide feed, a hydroxyl number of 168, and a primary hydroxyl content ofapproximately 38%.

Polyol C is a 3 functional, glycerin initiatedpolyoxyethylene-polyoxypropylene mixed feed polyol (8 wt. % EO) havingan equivalent weight of approximately 994 with a hydroxyl number of 56available from The Dow Chemical Company under the trade designationVORANOL® 3010 polyol.

Polyol D is a polyoxyalkylene copolymer polyol (CPP) containingdispersed polymer particles obtained by in-situ polymerization ofacrylonitrile and styrene with a hydroxyl number of 22 commerciallyavailable from the Dow Chemical Company under the trade designationVORALUX™ HL 431.

Polyol E is a 6.9 functional, polyoxyethylene-polyoxypropylene mixedfeed polyol (75 wt. % EO) having a hydroxyl number of 31, available fromThe Dow Chemical Company under the trade designation VORANOL® 4053.

Polyol F is a 3 functional, glycerine-initiated, cappedpolyoxyethylene-polyoxypropylene polyol (14% EO) having a hydroxylnumber of 34, available from The Dow Chemical Company under the tradedesignation VORANOL® 4701.

Polyol G is a 3 functional, glycerine-initiated all propylene oxidepolyether polyol with a hydroxyl number of 238, available from The DowChemical Company under the trade designation VORANOL® 2070

Monol is a poly propylene oxide—co-ethylene oxide monol, commerciallyavailable from The Dow Chemical Company under the trade designationUCON™ 50-HB-100.

Silicone A is a silicone surfactant used for viscoelastic MDI foams,commercially available from Momentive Performance Materials as NIAX™L-618 surfactant (a moderate surfactant designed for use with MDIfoams).

Silicone B is a silicone surfactant used for the stabilization ofconventional slabstock foam, commercially available from MomentivePerformance Materials as NIAX™ L-620 surfactant (a high performancealkyl-pendant type organosilicone surfactant designed for use inconventional flexible slabstock foams).

Amine catalyst A is a 70% bis-dimethylaminoethyl ether solution indipropylene glycol, commercially supplied as DABCO® BL-11 catalystavailable from Air Products and Chemicals, Inc.

Amine catalyst B is a 33% solution of triethylene diamine in dipropyleneglycol, available commercially from Air Products and Chemicals as DABCO33LV®.

Tin Catalyst is a stannous octoate catalyst, also known as tin(II)2-ethylhexanoate, available commercially from Evonik as KOSMOS® 29.

Polymeric MDI (PMDI) is polymeric MDI with a functionality of 2.2,commercially available as PAPI™ PB-219 from The Dow Chemical Company.

PMDI-2 is polymeric MDI with a functionality of 2.3, commerciallyavailable as PAPI™ 94 from The Dow Chemical Company.

Test Methods

Unless otherwise specified, the foam properties are measured by ASTMD3574.

EXAMPLE 1 TO 12 AND CONTROL (C1 to C6).

The samples in this study were made through box foaming using a 38 cm×38cm×24 cm wooden box lined with clear plastic film lining. A high shear16-pin (4 pins each in four radial directions) mixer at high rotationspeed was used. The pin mixer head was designed such that the ends ofthe pins are 1 cm clear of the wall of the 1-gallon cylindrical mixingcup. The components in the formulation with the exception of the tincatalyst and isocyanate were mixed first for 15 seconds at 2,400 rpm.Then the stannous octoate catalyst was added and immediately mixed foranother 15 seconds (2,400 rpm). Finally the isocyanate was added to themixture and immediately mixed for another 4 seconds (3,000 rpm). Theentire mixture was poured into the box lined with plastic film. The blowoff time was measured from the moment the final mixing step (the stepwith the addition of isocyanate) starts. Once foaming was complete, thefoam was further allowed to cure overnight under the hood. Foam samplewalls were discarded and the remaining samples were characterized formechanical and chemical analysis. Eleven formulations were studied andthe formulations and mechanical properties are provided in Table 1.

Foam samples were characterized according to ASTM D 3574. Table 1describes the formulations explored and the mechanical propertiesobserved for such formulations. The comparative example is labeled asC#1 and formulations of the embodiments described herein are labeled as#1-#12. Comparative example C#1 shows that compression set (39.7%) andair flow properties (0.37 I/s) of MDI based foams produced with an allPO polyol (Polyol A) and a copolymer polyol (Polyol D) is very poor.

EXAMPLES 13 TO 16.

A molded foam article was made using a high pressure impingement A-Bmixer, Cannon A-40, commercially available from a foaming equipmentmanufacturer, Cannon. A target mix-head pressure was about 1,500 psi forboth isocyanate (“A”) side and polyol (“B”) side. The isocyanate tankonly contains the polyisocyanate, and the polyol tank contains all thepolyols, surfactants, water and catalyst. The mixture was dispensed intoa heated aluminum mold with dimensions of 15″×15″×4.5″, with initialtemperature set at 49 degrees Celsius ±10 degrees Celsius, with eachshot completed in 5-7 seconds depending on the throughput. As shown inTable 2, very soft molded foam articles with good recovery performancewere obtained.”

The inventors have found that a significant improvement of compressionset and airflow properties for a viscoelastic polyurethane foam could beachieved by using a significant amount of EO-rich polyol (Polyol B) inthe reaction system. Formulation #1 demonstrates the use of a copolymerpolyol and a chain extender. Formulations #2 to 4 demonstrate the use ofa conventional high equivalent weight PO-rich polyol (Polyol C) with theuse of chain extender. Formulations #5 and 6 demonstrate the use ofmonol. Formulations # 7 to 11 demonstrate the use of the low equivalentweight PO-rich polyol (Polyol A), the EO rich polyol (Polyol B), and thehigh equivalent weight polyol (Polyol C) without the use of a copolymerpolyol, chain extender or monol. The examples demonstrate excellentcompression set properties, 90% CS <3% and the foam are open, most hashigh air flow >1 I/s.

TABLE 1 Formulations And Physical Properties. Formulation C1 1 2 3 4 5 67 8 9 10 11 12 Polyol A 80 20 30 25 20 25 25 25 25 20 17.5 15 Polyol B60 50 55 60 50 45 55 50 55 57.5 60 75 Polyol C 20 20 20 20 20 20 25 2525 25 25 Polyol D 20 20 Monol 5 10 Chain 0.75 0.75 0.75 0.75 0.75 0.750.75 Extender Water 2 2 2 2 2 2 2 2 2 2 2 2 2 Silicone 0.8 0.8 0.8 0.80.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 surfactant A Silicone 1 surfactant BAmine 0.2 0.2 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15catalyst 1 Amine 0.07 0.07 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.050.05 0.05 catalyst 2 Tin catalyst 0.05 0.05 0.05 0.05 0.05 0.05 0.050.05 0.05 0.05 0.05 0.05 0.05 Total 103.9 103.9 103.8 103.8 103.8 103.8103.8 103.1 103.1 103.1 103.1 103.1 103.3 Polymeric 50.06 47.4 48.2 48.248.2 47.74 52.3 46.61 45.65 45.65 45.65 45.65 45.8 MDI Total A + B 153.9151.3 152.0 152.0 152.0 151.5 156.1 149.7 148.7 148.7 148.7 148.7 149.1Iso Index 78 75 75 75 75 75 83 75 75 75 75 75 75 Airflow (l/s) 0.37 1.090.76 1.37 1.89 0.93 0.078 1.07 1.48 2.33 2.42 2.35 2.68 90% CT 39.7 1.21.9 1.3 1.1 1.9 2.5 1.3 1.6 1.1 1.1 0.9 1.2 (%) Density 51.2 52.4 50.950.9 51.3 51.1 49.7 47.9 48.0 48.8 48.4 48.2 47.9 (kg/m³) Recovery 3 2 22 2 3 6 2 3 2 2 2 time (s) Resiliency 8 3 1 1 2 5 2 3 2 2 3 3 4 (%) Tear175 136 135 128 149 114 150 128 173 161 169 171 114 Strength (N/m)Elongation 95 113 139 143 134 151 141 141 178 188 195 191 (%) 25% IFD 2314 11 10 10 8.5 13 11 8 8 7 8 (lbf) 65% IFD 60 26 22 20 21 17 26 22 1616 16 17 (lbf) 40% CFD 0.9 (kPa)

TABLE 2 Formulation and Physical Properties. Ex. 13 Ex. 14 Ex. 15 Ex. 16Formulation Polyol A 15 20 20 0 Polyol B 45 50 50 60 Polyol E 25 15 15 5Polyol F 15 15 15 20 Polyol G 0 0 0 15 Water 2.7 2.5 2.7 2.6 Silicone A1 1 1 0.7 Amine A 0.15 0.15 0.2 0.15 Amine B 0.3 0.2 0.2 0.27 Total89.15 83.85 84.10 103.72 Index 60 60 65 70 PMDI-2 39.44 39.59 44.7835.45 Grams 1150 1150 1050 1400 Wt Foam 937 922 855 807 Properties 90%Comp. 8 n/a n/a n/a 50% Comp. n/a 30 2 4 Ten. Str. 4.3 3.0 4.8 n/a %Elong. 86 82 86 n/a Tear Str. 0.35 0.36 0.48 0.60 Resil. n/a n/a n/a n/aAir Flow 0.88 0.47 n/a 1.47 Density 3.7 3.6 3.5 3.2 Recovery Time (Sec)2 3 3 2 CFD 25% 1.9 1.7 1.9 2.0 CFD 65% 3.5 3.1 3.5 3.4 CFD 75% 5.9 5.35.8 5.6 Support Factor(%) 1.80 1.86 1.83 1.76 Comments very slow

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof.

1. A reaction system for preparation of a viscoelastic polyurethane foamcomprising: (a) an organic polyisocyanate; and (b) an isocyanatereactive component comprising: (i) from 10 to 50% by weight of theisocyanate reactive component of one or more low equivalent weightpropylene oxide rich (PO-rich) polyols having a combined number averageequivalent weight from 200 to 500; (ii) from 45 to 95% by weight of theisocyanate reactive component of one or more ethylene oxide (E0-rich)polyols having a combined number average equivalent weight from 200 to800 and an ethylene oxide content from 30% to 75% by weight of the totalmass of the EO-rich polyol; and at least one of (iii) from 10 to 30% byweight of the isocyanate reactive component of one or more highequivalent weight propylene oxide rich (PO-rich) polyols having a numberaverage equivalent weight from 800 to 2,000; and (iv) from 10 to 40% byweight of the isocyanate reactive component of one or more propyleneoxide co-polymer polyols containing styrene-acrylonitrile.
 2. Thereaction system of claim 1, wherein the one or more EO-rich polyols havean ethylene oxide content from 45% to 60% of the total mass of theEO-rich polyol.
 3. The reaction system of claim 2, wherein the one ormore EO-rich polyols have a primary hydroxyl content of less than 50%.4. The reaction system of claim 1, wherein the isocyanate reactivecomponent further comprises: (v) from 5 to 10% by weight of theisocyanate reactive component of one or more ethylene oxide-propyleneoxide monols having a combined number average equivalent weight from 300to
 800. 5. The reaction system of claim 4, wherein the isocyanatereactive component further comprises: (vi) a chain extender.
 6. Thereaction system of claim 5, further comprising: (c) water; and (d) acatalyst component.
 7. The reaction system of claim 6, furthercomprising: (e) an organosilicone surfactant.
 8. The reaction system ofclaim 7, wherein the one or more ethylene oxide-propylene oxide monolshave a functionality between 1 and 2 and a combined number averageequivalent weight from 400 to
 600. 9. The reaction system of claim 8,wherein the one or more ethylene oxide-propylene oxide monols have anethylene oxide concentration that is between 30-70% by weight of thetotal mass of the monol.
 10. The reaction system of claim 1, wherein theone or more ethylene oxide (EO-rich) polyols comprises from 70% to 95%by weight of the isocyanate reactive component of the one or moreethylene oxide (EO-rich) polyols having a combined number averageequivalent weight from 200 to 800 and an ethylene oxide content from 40%to 65% of the total mass of the EO-rich polyol.
 11. A method ofpreparing a viscoelastic foam, comprising: forming reaction components,comprising: an organic polyisocyanate; an isocyanate reactive componentcomprising: one or more low equivalent weight propylene oxide rich(PO-rich) polyols having a combined number average equivalent weightfrom 200 to 500 comprising from 10 to 50% by weight of the isocyanatereactive component; one or more ethylene oxide (EO-rich) polyols havinga combined number average equivalent weight from 200 to 800 and anethylene oxide content from 40% to 65% by weight of the total mass ofthe EO-rich polyol comprising from 45 to 95% by weight of the isocyanatereactive component; and at least one of one or more high equivalentweight PO-rich polyols having a number average equivalent weight from800 to 2,000 comprising from 10 to 30% by weight of the isocyanatereactive component; and one or more propylene oxide co-polymer polyolscontaining styrene-acrylonitrile from 10 to 40% by weight of theisocyanate reactive component; water; and a catalyst component; andcombining the reaction components at conditions sufficient to form aviscoelastic polyurethane foam.
 12. The method of claim 11, wherein theone or more EO-rich polyols have an ethylene oxide content from 30% to75% of the total mass of the EO-rich polyol.
 13. The method of claim 12,wherein the one or more EO-rich polyols have a primary hydroxyl contentof less than 50%.
 14. The method of claim 13, wherein the isocyanatereactive component further comprises: (v) from 5 to 10% by weight of theisocyanate reactive component of one or more ethylene oxide-propyleneoxide monols having a combined number average equivalent weight from 300to
 800. 15. The method of claim 14, wherein the isocyanate reactivecomponent further comprises: (vi) a chain extender.
 16. The method ofclaim 15, further comprising: (e) an organosilicone surfactant.
 17. Themethod of claim 16, wherein the one or more ethylene oxide-propyleneoxide monols have a functionality between 1 and 2 and a combined numberaverage equivalent weight from 400 to
 600. 18. The method of claim 17,wherein the one or more ethylene oxide-propylene oxide monols have anethylene oxide concentration that is between 30-70% by weight of thetotal mass of the monol.
 19. The method of claim 18, wherein the one ormore ethylene oxide-propylene oxide monols have an ethylene oxideconcentration that is between 40-60% by weight of the total mass of themonol.